1. Field of the Invention
The present invention relates to a vehicle for use on inclined ground in a mountainous region or the like for such purposes as carrying felled timber. More particularly, the invention pertains to a vehicle for use on inclined ground in which the vehicle body, such as a deck, is supported on a chassis frame which is provided on both sides with wheels or crawlers which constitute propelling means in such a manner that the center of gravity of the vehicle body is movable.
2. Description of the Prior Art
Known prior arts related to the present invention include various types of suspension, that is, the pendulum suspension in which a vehicle body is pivotally connected to a chassis frame through a center pin as shown in FIG. 7, the parallelogram type shown in FIG. 8, and the type in which the vertical location of the wheels is changed as shown in FIG. 9. These prior arts, however, have advantages and disadvantages in terms of the distribution of weight on the crawler on the higher side (referred to as the "higher crawler", hereinafter) and the crawler on the lower side (referred to as the "lower crawler", hereinafter), and further, the ground conditions of the crawlers in states wherein the chassis frame is inclined.
The advantages and disadvantages of the prior arts will be described hereinunder in detail.
The pendulum suspension shown in FIG. 7 has the advantage that the crawlers invariably contact the ground over their entire lower surfaces when the chassis is inclined. However, since the center of gravity of the vehicle body is positioned on the perpendicular line n which passes through the center pin, this perpendicular line intersects the surface of the ground at a position closer to the lower crawler than the position at which the center line m which passes through the center point between the right and left crawlers intersects the surface of the ground at right angles. In more understandable terms, since the respective weights of both the chassis and the vehicle body are positioned on the downhill side, the sum total of these two weights acts on the vehicle in the downhill direction. As a result, the higher crawler has a lighter load than the lower crawler, which fact undesirably produces a difference in traction between the two crawlers, resulting in such problems as reducing the performance of the machine, risk of sideslip and damage to the surface of the ground.
On the other hand, the parallelogram type suspension shown in FIG. 8 and the suspension type wherein the vertical location of wheels is changed, shown in FIG. 9, have the advantage that the weight of the vehicle body is substantially uniformly distributed over the right and left crawlers even in a state wherein the chassis is inclined. However, in such a case, the area of contact of each crawler with the ground is undesirably decreased, and the ground pressure rises unfavorably, which fact disadvantageously involves the attendant risks of reducing traction, erosion of the ground and possible sideslip of the vehicle.